Electric control apparatus for fuel burners



an 6K '7 'A. L. W551; 2,064,181

Kg ha/M than Dec. 15, 1936 Abraham, Lincoln Rube], Des Moines, Iowa,

signor to Penn Electric Switch 00., Des Moines, I .Iowa, a corporationof Iowa Application August 15, 1932, Serial Nmszassa An object of myinvention'is "to provide control apparatus for the electric circuit ofafuel burner, the apparatus'being comparatively "simple and inexpensiveto manufacture.

A further object is tofprovide control apparatus including'a warp switchwhich is energized when combustion occurs in order to break the circuitthrough a'heater of a safety switch, so that upon combustion] occurring;the safety switch will not thereafter trip out.' r

' Still a further object'is to provide means whereby the safetyswitchcanfbe. used to tripout for the purpose of providing a lock outtype control in which combustionfailure itself has the effect ofshuttingdown the automatic operation of the device.

Stillafurther objectis to rearrange the circuits and contacts slightlyso that after combustion failure, a purging period is provided andthenthe control apparatus is re-cycled for automatic operation. r, v

Still a furtherobject is to provide control apparatus including a relaywhich initiates and terminates operation of a fuel burner and whichinitiates operation of ignition mechanism for the fuel burner,termination of the operationofthe ignition mechanismbeing effected bycombustion occurring.

Still a further object is-to providea control apparatusin which a safetyswitchfiheater, a warp switch and a relay are all -in.circuit with eachother, acombustion responsive switch being effective to'open the safetyswitch heater circuit and-energizev a warp switch heater which warps theswitch to a position where it shunts the relay out of the'circuitso thatupon combustion failure, current will ,flowthrough the safety switchheater, but not through the relay,

with the effect of quickly heating the safety switch rheaten-totrip itand thus lock the apparatusin non-operating position. .1-

- Stilla further objectis to provide another apparatus in which therelay is not shunted out,

but the warp switch, upon combustion failure. is

allowed tdreturn to initial position for recycling the apparatuasuchreturn being slow so as'to provide a purging period.

Boththe lock out type andthe purgingperiod type of apparatus are used ona fuel burner so that upon combustion failure occurring, such as causedby a down draft in the-furnace, a slug of-waterin the fuel oil or thelike, automatic operation of the apparatus willeither' stop until thecause has been remedied and the apparatus ---indicated as I, 2,

. son-inns. (01. 158-28 & cycle after a purging period has been providedto allow the draft of the furnace to purge the combustion chamber of anyexplosive gas caused bythe introduction of fuel after combustion fails.

With these and other objects in view my invention consists in theconstruction, arrangement and'combination of the various parts a: my device, whereby the objects contemplated are attained, as hereinafter morefully set forth, point- '10 ed out in my claims, and illustrated inthe'ac- .companyingdrawing, in'which:

Figure -1 is an electrical diagrammatic view showing mylock out type ofcontrol apparatus;

reset,;or-it will re- .ing period'type of apparatus. D

On the accompanying drawing, I have 'used the reference numeral It toindicate a' line switch. A limit switch is shown at l2 which maybe tem-20 -perature or steam pressure operated and which is'ordinarily used incontrol circuits on furnaces 'an'dboilers to prevent the furnace orboiler being heated to an excessivedegree. Junction boxes 15 1 Figure 2is a' similar figure showing the purg- -'are shown at I 4 and I6."'I'hese'form no essential 25 part of my present invention, but aremerely provided on the. actual switch for [the convenience of theelectrician when installingand wiring the apparatus. The

junction box l6 v v r 3 and L I do My apparatus further includes a roomthermostat l 8, aicombustionresponsive'control switch 20, n ignitionswitch 22 also responsive to combushas 4 terminals tion; a safety switch24, a warp switch 26 and a relay'28. At 30 a furnaceis shown and theburnertherefor is shown more or less diagrammatic at '32. An ignitiontransformer is shown at 34, and a spark gap at 36. This comprises theignition mechanism mentioned in my claims.

In Figure 1, the control switch'2ll has contacts 40 38, t0 and", Theignition switch 22 has contacts '44 and 4 6. The safety switch 2lhascontacts 48 and 50, "The-safety switch includes a heater 52 and abimetal latch, which, when warped to the dotted line position by. heatfrom the heater 52, 45 Q'will permit disengagement ofthe contacts '48and "50. The warp switch 26 includes contacts, 58 and 60. The warpswitch further includes a bimetai actuator 62 for the contact 56 andawarp switchheater 64." Y a 50 In. Figure 2, the control switch 20 hascontacts '38, 4| and '42. The ignition switch has contacts and l6 3elsafety switch and the warp switch 26 are the same as in Figure lexceptthere ism contact 58. P '55 -the heater II.

J2 so that itwill v Y which wouldoccurafter a period of time if com- Therelay 28 has burner control contacts 06 and 68 and holding contacts 10and. l2.

The control and ignition switches Ill and I! in both figures arenormally in the solid line positions; Upon combustion occurrin8, bimetalhelixes 2| cause movement of the contacts 38 and 4G to their dotted linepositions. Thecombustion responsive switches 2. and 22 are of theordinary type commonly termed a stack switch having a slip connection tocause immediate movement of the movable contacts from one position toanother and thereafter permitting slippage. The warp switches 28, whenheated by energization of the heater 64, warp to the dotted linepositions.

In conjunction with my apparatus, I provide a transformer 14 having a-primarywinding "and a secondary low voltage winding ll, so that therelay and the mechanism for controlling it therefore need not beconstructed for high voltage current.

Operation of lock out control apparatus Referring to-Figure 1, the roomthermostat I! I is in open position.

, I when it calls for heat, the current may be traced from the secondarywinding 18, through the room thermostat is, through the closed contacts3! and 40, throughthe safety switch heater 5!, through the warp switch26 and its contacts 5 and it and through part of the relay 28 andreturn. This energizes the relay so that its armature 280. isattractedito'the dotted line position, whereupon highvoltage currentfrom the left side of the line switch It, through the limit switch II,the safety switch 24 and the contacts 68 and 68 flows to the burner 32and return. Also, the high voltage current flows from the contact II,through the ignition contacts 44 and "to the ignition transformer andreturn. This causes'a high tension spark at the spark gap 36.Energization of the relay 28 also, closes the contacts "l0 and I! sothat currentfrom the room thermostat II is supplied through the entirecoil of the relay 2. and return. Thus the. relay is held in closedposition after once being energized.

Upon combustion occurring, the contacts 38 and 4| of the control switch2|! are separated for opening the circuit through the safety switchheater not open the safety switch 24,

bustion did not separate the contacts. the firstcircuit through therelay 28, but the holding contacts It and I! retain the relay inenergized position. Combustion occurringalso separates the ignitioncontacts 44. and to terminate operation of the ignition mechanism.Combustion occurring also closes the contacts 38 and 42 of the controlswitch 20 which energizes the warp switch heater 64. This will cause theswitch 2' to warpto the dotted line position, engaging contact 56 withcontact 54.

Subsequently, upon combustion failure, the contact "will re-engagethecontact 4| for'energlzing the safetyswitch heater I2 without passingthe current through the relay coil It because the contacts "-40. areclosed amaterial time period before the warp element 62 has cooledsuihciently to open the contacts 4 and in the circuitof This results ina much quicker heating of the heater is m immediately nlhg the safetyswitch 24 contacts due to the fact that there is less resistance inseries with the heater. The

apparatus is now locked out inasmuch-as it cannot here-cycled exceptafter-the safety switch 24 has beenmanually reset.

' tion establishment also .64. Thereafter the heater warp switch. 26. Itwill eliminated.

This opens In Figure 2, closing of'the contacts in the room thermostatII will establish a circuit through the safety switch heater 52, thewarp switch It and its contacts 50 and 80, the. relay 28 and return.This initiates operation of the burner and of the ignition mechanism,termination of the ignition mechanism being tacts 44 and 48, the same asin Figure 1.

Upon combustion establishment, the contact ll engages thecontact 4| forestablishing the holding circuit through the contacts 10 and 12 whichhave been engagedby energization of the relay 2!; but not renderedeflective becauseof the normal full line positionsof thecontacts I8 and4 I. Combuscloses the circuit through contacts 38 and 42 for energizingthe warp switch heater 64 and causing the warp switch 26, to warp to itsdotted line position. This'opens the circuit through the safety switchheater 52.

Upon combustion failure, the contact 38 separates from the contacts 4|and 42, thus de-energizing the holding circuit through the contacts "and12 for terminating operation of the bumer I: and de-energizing the warpswitch heater V 64 will gradually cool down and so will the bimetalelement 62 of the finally cause engageand 00 which re-estabthe upperportion of the ment of the contacts 56 lishes a circuit through relaycoil tore-cycle the apparatus by re-initiating operation of the burner".The period of time during which the bimetalelement 62 moves from thedottedline to the full line position provides a period during which thefurnace is purged of gases which might explode whenthe contacts 66 and6B are re-engaged tore-establish ignition as well as re-initiateoperation of the burner. g

'In either form of my apparatus, I provide a warp switch for opening thesafety switch heater circuit and for controlling the circuit so thateither a lock out (in Figure 1) or a purging period operation results(in Figure 2). Although I have shown the transformer 14, it will beobvious that the entire apparatus maybe operated by high voltage currentSome changes may be made in. the construc-. tion and arrangementof theparts of my device without departing from the real spirit and purpose ofmy inventiomandit is my intention to cover by my claims, any modifiedforms of struc ture or use or mechanical equivalentawhich may bereasonably included. within their scope.

-I claim as 'my invention: 2. 1. In combination with an electricallyoperated ;fuel burner,-a control system comprising a.

' relay operable when energized to close the burner circuit to initiateoperation, 'a room thermostat controlling energization of said relay, 9.thermal time limit cutout switch including a resistance heatercontrolling said system, a switch having a warpelement, a heater, firstcontacts which, are closed when .said element is cold and'contacts'whichare closed when said element is and the transformerheated, combustion responsive switching means 1 having contacts closedin the. absence of combustion and other contacts closed inthe presenceof combustion, a circuit including the room ther-,

mostat', the contacts of the combustion ,responsive switching meansclosed. in the absence ofcombustio ,the cutout switchheater, said firstcontacts and said relay, a second circuit-including the heater for saidwarp element and the contacts of the combustion responsive switchingmeans closed in the presence of combustion and a third circuit includingthe heater of said cutout switch and said second contacts, said warpelement moving slowly when cooling whereby upon combustion failure, saidcutout switch is quickly actuated to shut down the system.

2. In combination with an electrically oper ated fuel burner, a controlsystem comprising-a relay operable when energized to close the burnercircuit to initiate operation, a room thermostat controllingenergization of said relay, a thermal time limit cutout switch includinga heater controlling said system, a switch having a warp element, aheater, first contacts which are closed when said element is cold andsecond contacts which are closed when said element is heated, combustionresponse switching means having contacts closed in the absence ofcombustion and other contacts closed'in the presence of combustion, acircuit inluding the room thermostat, the contacts of the combustionresponsive switching means closed-in the absence of combustion, thecutout switch heater, said first contacts and said relay, said relayhaving holding contacts to maintain the relay energized when saidcontacts of the combustion responsive switching means closed in theabsence of combustion areopened by'the presence of combustion, a secondcircuit including the heater for said warp element and the contacts ofthe combustion responsive switching means closed in the presence ofcombustion and athird circuit including the heater of said cutout switchand said second contacts, said warp element moving upon combustionfailure, said cutout switch is quickly actuated to shut down the system.

3. In a system having electrically controlled fuel feeding and ignitionmeans, a main control switch, an electrically actuated time limit cutoutswitch operable to open in time periods varying in accordance with itsrate of energization, switching mechanism including reactances and acombustion controlled switch, and circuit connections including theforegoing elements controlling energization of the fuel feeding andignition means and the energization of the time switch and rate thereofand operable upon a demand for heatand closure of the main switch to:(1) energize the fuel feeding and ignition means and energize thetimeswitch at a predeslowly when cooling whereby terminedrate; (2)'deenergize the ignitionmeans and time switch upon the establishment ofcombustion; higher the fuel feeding during normal op'eratim. 4. Incombination with its fuel feeding means, a control system includand (3)reenergize the time switch at a rate while maintaining energization ofmeans upon a failure of flame a fluid fuel burner and ing in circuit amain control member, an electril cal safety time switch whose timinginterval varies with the rate at clusion of the timing interval, acombustion responsive device, and meansresponsive to the main controlmember for simultaneously initiating operation of said burner andenergizing said time switch at a first rate, and cooperating with thecombustion responsive device to deenergize said time switch upon thesuccessful establishment of combustion, and to ree'nergize said timeswitch ata second rate higher than said'flrst rate upongthe occurrenceofsubsequent flame failure, whereby said time switch provides a longer,timing interval upon initiation of operation of the burner than isprovided upon the occurrence of flame failure.

5. In a system having electrically controlled fuel feeding and ignitionmeans, a main control switch, an electrically actuated time limit cutoutswitch operable to open in a time period varying in accordance with therate of current flow therethrough, a plurality of switches, switching.mechanism for actuating reactances and a combustion responsivethermostat, and circuit connections including the 10 I which it isenergized for 4 discontinuing fuel feed to the burner at thereonsaidswitches including? foregoing elements controlling energization of andfeeding and ignition,

rate; (2) de -enure duringnormal operation to re-e'nergize said, I

time'switch at a relatively high'rate while maintaining energization ofthe fuel feeding means whereby said time switch will quickly. open torender the system inoperative.

ABRAHAM Lmcom RUBEL. r

